The Relationship of Some Glycosidases to the Endogenous and IAA-induced Growth of Light-grown Cucumber Hypocotyls

Some glycosidases in light-grown cucumber (Cucumis sativus L. cv. Aonaga-jibae) hypocotyl sections were examined with respect to their localization and relation to endogenous and IAA-induced growth. Frozen-thawed sections were used directly for measurement of enzyme activities, and β-glucosidase, α- and β-galactosidases and β-xylosidase were assayed by using p- or o-nitro-phenylglycopyranosides as substrates. The order of the activity of these enzymes were β -glucosidase > β -galactosidase =α-galactosidase > β-xylosidase. No activity of α-glucosidase was detected. High glycosidase activities were found in the youngest region of the hypocotyl, where the endogenous growth rate was highest. However, there was no significant difference in the activities of this region between seedlings at different growth stages. Among the enzymes tested, β -glucosidase showed a high correlation with the endogenous growth rate. β-glucosidase was found to be mostly associated with the cell wall fraction, while β-galactosidase was rather found in the soluble fraction of the cell. Separation of the epidermis from the section showed that a very high activity of β-glucosidase was associated with the epidermis. In both whole sections and isolated cell wall fractions, IAA was shown to have no effect on the activities of β-glucosidase and β-galactosidase.     

Ammonia Release by Chum Salmon Eggs at the Initiation of Their Embryonic Development

We have found that inseminated eggs of the chum salmon, Oncorhynchus keta , actively release alkaline substances when they have been stimulated by deionized water; the pH of the egg suspension prepared in the non-buffered Salmon-Ringer solution shifts within at least 1.3 pH units. The nesslerization method and an ammonia gas sensitive electrode measurement reveal that the alkalization of the suspension is partly due to the efflux of ammonia from the stimulated eggs. The increase in the intracellular ammonia level leading to the alkalization of ooplasm may occur at an early stage of the embryonic development. Since the ammonia release is observed also in the eggs stimulated parthenogenetically by deionized water, it can be inferred that the stimulation of the egg triggers a reaction which increases the ammonia level in the ooplasm.
The environmental medium of stimulated eggs contains fairly large amounts of organic compounds. Its UV spectrum shows a peak at 249 nm; the position of the absorption maximum corresponds to that of inosine monophosphate (IMP). This fact suggests that IMP is one of the components of the organic compounds. The presence of IMP in the medium is also shown by thin layer chromatography. The medium contains monosaccharides and peptides. We have explained these results by postulating that an abrupt change in the activity of adenylate deaminase which catalyzes the conversion of adenosine monophosphate to ammonia and IMP occurs at the initiation of the embryonic development in the chum salmon egg.